Extended duration autonomous craft

ABSTRACT

Autonomous craft capable of extended duration operations as lighter-than-air craft, having the ability to alight on the surface of a body of water and generate hydrogen gas for lift via electrolysis using power derived from a photovoltaic system, as well as methods of launching an unmanned aerial vehicle (UAV) having a deployable envelope from a surface of a body of water.

FIELD

This disclosure relates to autonomous craft capable of travel on wateror in the air, and more specifically to autonomous craft capable ofextended duration operation.

BACKGROUND

Unmanned vehicles, including Unmanned Aerial Vehicles (UAV or drones),Unmanned Surface Vehicles, and Unmanned Underwater Vehicles, have provenuseful for a wide variety of commercial, scientific, and militaryapplications. However, such vehicles are typically used for relativelyshort-duration missions, partly due to the constraints of carryingsufficient fuel for extended missions, and partly due to the need forremote piloting of the vehicle. Therefore, in order to enhance utilityfor very long duration applications, such vehicles should besubstantially autonomous, and able to operate without requiring frequentrefueling.

Some unmanned vehicles have been used as long-term platforms when mooredin place, or even permitted to drift on the water's surface or in theatmosphere, the lack of directed mobility may critically limit thecapabilities of such platforms.

What is needed is an autonomous vehicle capable of powered flight thatis additionally able to refuel autonomously and in the absence of afueling infrastructure.

SUMMARY

The present disclosure provides autonomous craft capable of extendedduration operations as lighter-than-air craft by having the ability tofloat on the surface of a body of water and generate hydrogen gas forlift via electrolysis using power derived from a photovoltaic system.The disclosure further provides methods of launching an unmanned aerialvehicle (UAV) having a deployable envelope from a surface of a body ofwater.

In some aspects, the disclosure may provide an autonomous craft thatincludes a hull structure configurable to support the craft on thesurface of a body of water; an inflatable envelope coupled to the hullstructure that is capable of containing an amount of hydrogen gassufficient to render the autonomous craft lighter-than-air; a storagebattery configured to store electricity received from an electricalnetwork and discharge electricity into the network; a photovoltaicsystem having one or more photovoltaic panels that is coupled to theelectrical network and configured to generate electricity from light; anelectrolysis apparatus coupled to and powered by the electrical networkthat can electrolyze ambient water and generate hydrogen gas when thecraft is near to or on the surface of the body of water; a hydrogen gashandling system that can compress and store the generated hydrogen gasin a storage tank, release the compressed hydrogen gas into theinflatable envelope, and to compress and store hydrogen withdrawn fromthe inflatable envelope in the storage tank; and a processing systemthat can control the electrical network, the photovoltaic system, thestorage battery, and the electrolysis apparatus. The processing systemof the autonomous craft may be further configured to control thebuoyancy of the autonomous craft by varying the amount of hydrogen inthe envelope.

In some aspects, the disclosure may provide an autonomous craft thatincludes a vessel configured to alternately float upon a water surfaceand to float aloft as a lighter-then-air craft using a hydrogen gassupply for buoyancy, where the vessel includes a photovoltaic array forproviding power and an electrolysis apparatus for electrolyzing waterwhile floating on the water surface in order to replenish the hydrogengas supply.

In some aspects, the disclosure may provide a method of launching a UAVhaving a deployable envelope from a surface of a body of water, themethod including electrolyzing water from the body of water to generatehydrogen gas, adding the hydrogen gas to the deployable envelope toincrease the buoyancy of the UAV, and lifting the UAV from the surfaceof the body of water.

The recited features, functions, and advantages of the disclosed devicesand methods may be achieved independently in various aspects of thepresent disclosure, or may be combined in yet other aspects furtherdetails of which can be seen with reference to the following descriptionand drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a depiction of an illustrative autonomous craft according tothe present disclosure traveling on the surface of a body of water,above the surface of the body of water, and beneath the surface of thebody of water.

FIG. 2 is a depiction of an illustrative autonomous craft according tothe present disclosure.

FIG. 3 depicts the illustrative autonomous craft of FIG. 2 having adeployed inflatable envelope.

FIGS. 4A-4C schematically depict cross-sectional views of the envelopecompartment of an autonomous craft as an inflatable envelope isretracted and stored. FIG. 4A shows the envelope anchored and deployed.FIG. 4B shows the envelope being deflated and reeled in. FIG. 4C showsthe envelope fully stowed.

FIG. 5 schematically depicts the power generations and distributionsystem of the autonomous craft of the present disclosure.

FIG. 6 schematically depicts the hydrogen generation and handling systemof the autonomous craft of the present disclosure.

FIG. 7 schematically depicts the processing system of the autonomouscraft of the present disclosure.

FIG. 8 is a flowchart depicting an illustrative method of launching anunmanned aerial vehicle according to the present disclosure.

DESCRIPTION

Various examples of autonomous craft having one or more advantageousproperties are described below and illustrated in the associateddrawings. Unless otherwise specified, the disclosed autonomous craftand/or methods including the disclosed autonomous craft may, but are notrequired to, contain at least one of the structure, components,functionality, and/or variations described, illustrated, and/orincorporated herein. Furthermore, the structures, components,functionalities, and/or variations described, illustrated, and/orincorporated herein in connection with the present teachings may, butare not required to, be included in other autonomous craft or UAVs.

The following description of various such examples is merely exemplaryin nature and is in no way intended to limit the disclosure, itsapplication, or uses. Additionally, the advantages provided by theexamples, as described below, are illustrative in nature and not allexamples may provide the same advantages or the same degree ofadvantages.

FIG. 1 depicts an illustrative autonomous craft or vessel 10 accordingto the present disclosure that is configured to be capable of restingand/or traveling upon a surface of a body of water 12 as a surface craft(A), capable of floating aloft as a lighter-than-air craft (B), andadditionally or alternatively capable of submerging and/or traveling asa submersible craft (C). Autonomous craft 10 may be configured to employhydrogen gas to generate lift in order to travel aloft, and maytherefore be capable of performing extended duration missions bydescending to the surface 12 and replenishing its hydrogen gas supplythrough the electrolysis of collected water.

An exemplary and illustrative autonomous craft 10 is depicted in FIG. 2,and craft 10 may include one or more of a variety of components andsystems in order to enable or facilitate the intended operation of thecraft, as shown in FIGS. 2-7.

Craft 10 includes a hull structure 20 that is configured or configurableso that craft 10 can be supported on a surface of a body of water. Asshown in FIG. 2, craft 10 includes two pontoon members 22 and a cabinstructure 24 extending between pontoons 22. Although depicted as havingtwo pontoon members 22, autonomous craft 10 may incorporate any suitablehull structure that facilitates floating or traveling on a watersurface, including single hulls (such as flat-bottomed, v-bottomed, androunded hulls), or multi-hulls (such as catamarans, trimarans, and thelike). The hull structure 20 may incorporate both rigid and inflatableportions, such as for example used for ZODIAC inflatable boats (ZodiacNautic), although a purely rigid hull design may offer greaterdurability.

Craft 10 may further include an inflatable envelope 26 that is securelycoupled to the hull structure 20. Envelope 26 is configured so that itis capable of containing an amount or volume of hydrogen gas that issufficient to render the autonomous craft 10 lighter-than-air. That is,craft 10 may be configured so that when envelope 26 is inflated withsufficient hydrogen gas to offset the weight of the craft, it may ascendvertically as a lighter-than-air craft, suspended from envelope 26 in amanner similar to the gondola of a balloon.

Craft 10 is depicted suspended from envelope 26 in FIG. 3. When not inuse, envelope 26 is stowed within cabin structure 24. When inflated,envelope 26 is coupled to craft 10 at envelope coupling 27, whichincludes the valves and plumbing for adding and removing hydrogen fromthe envelope, as well as supporting some of the weight of craft 10.Envelope 26 is also attached to craft 10 at the forward end of cabinstructure 24 via a reel mechanism 28, which serves to help retract andstow envelope 26 when not inflated.

The portion of cabin structure 24 used to stow envelope 26 is shown incross-section in FIGS. 4A-4C. In FIG. 4A envelope 26 is fully deployed.When it is desirable to deflate and stow envelope 26, hydrogen isremoved from envelope 26 at the same time that reel mechanism 28 beginsto turn, thereby rolling up envelope 26, as shown in FIG. 4B. Reelmechanism 28 may include conical endplates in order to help guideenvelope 26 around reel 29 as the envelope deflates. At the same time,the doors 30 of the envelope compartment 31 may be opened at an anglethat further guides the envelope into position for stowing as itdeflates. As shown in FIG. 4C, once envelope 26 is fully deflated andreeled completely around reel 29, the envelope is stowed in the envelopecompartment, and the doors 30 can be closed. To deploy envelope 26, theenvelope is inflated with hydrogen gas as reeling mechanism 28 isreversed, feeding envelope off the reel.

Alternatively, or in addition, envelope 26 can incorporate or featureso-called ‘soft origami’ features to enhance deployment and stowing ofthe envelope (see for example Bruton et al., R. Soc. open sci. 3: 160429(2017)). Balloons suitable for long-duration and/or high-altitudeapplications have been developed previously, see for example Google'sProject Loon.

It should be appreciated that coupling 27 and reel mechanism 28 areconstructed sufficiently robustly that the full weight of craft 10 maybe suspended from envelope 26 when aloft.

Craft 10 may additionally include a power generation and distributionsystem 32, which is shown schematically in FIG. 5. Any method of powergeneration with sufficient capacity to meet the needs of craft 10 is asuitable method of power generation, provided that the power generationsystem is sufficiently compact and/or lightweight to facilitate theability of craft 10 to travel aloft.

In one aspect of the disclosed craft, the power generation anddistribution system includes a photovoltaic system 33 having one or morephotovoltaic panels 34, that are configured to generate electricity fromlight that is incident upon the photovoltaic panels. The photovoltaicpanels 34 may be disposed on any suitable exterior surface of craft 10,such as on the upper surface of cabin structure 24, or on the doors 30of the envelope compartment 31. However, it may be particularlyadvantageous to place photovoltaic panels 34 on the exterior of envelope26 as shown in FIG. 3, so that when envelope 26 is deployed duringdaylight hours, electricity may be generated.

The power generation and distribution system 32 may include a storagebattery 35 that is electrically coupled to the photovoltaic system 33and configured to receive and store electricity generated byphotovoltaic system 33. Storage battery 35 may be further configured todischarge stored electricity in order to power various other systems ofcraft 10 via an electrical network 36 that couples the photovoltaicsystem 33 to storage battery 35, as well as coupling battery 35 to theone or more additional components of craft 10 that may requireelectricity, as shown in FIG. 5

Electricity supplied by power system 32 may be used to operate anelectrolysis apparatus 38 which may be coupled to electrical network 36.Electrolysis apparatus 38 may be configured to electrolyze ambient waterin order to generate hydrogen gas, for example, ambient water may beobtained from a body of water on which craft 10 may be floating.Electrolysis apparatus 38 may obtain ambient water via a probe or diptube that is configured to be lowered into the body of water throughwhich ambient water may be aspirated into electrolysis apparatus 38 asneeded. Alternatively, or in addition, an ambient water port may beincorporated into one of pontoon members 22, so that when craft 10 isafloat the water port will be in contact with ambient water which may bepumped to the electrolysis apparatus.

Craft 10 may incorporate a hydrogen gas handling system 40 that isconfigured to compress and store the hydrogen gas generated byelectrolysis apparatus 38. Hydrogen gas handling system 40 may includethe compressors and pumps necessary to move and store compressedhydrogen gas in one or more hydrogen storage tanks 42. Additionally,hydrogen gas handling system 40 may be configured to remove hydrogen gasfrom storage tank 42 and controllably add it to envelope 26 in order togenerate lift, and similarly, to remove hydrogen gas from envelope 26and compress the hydrogen gas to store in storage tank 42, reducing theaerial buoyancy of craft 10. Hydrogen gas may be moved where needed viaa hydrogen gas manifold 44, as shown schematically in FIG. 6. As shownin FIG. 2, a hydrogen tank 42 may be disposed within one or both pontoonmembers 22.

As craft 10 includes an onboard supply of hydrogen, the power generationand distribution system 32 may include an auxiliary source of powergeneration that is a hydrogen fuel cell 45 that is configured togenerate electricity via an electrochemical reaction between hydrogengas stored onboard and oxygen, where the oxygen may be captured byelectrolysis apparatus 38 or removed from the atmosphere as needed. Forthermodynamic reasons, it would be impractical to use hydrogen fuel cell45 to power electrolysis apparatus 38. However, fuel cell 45 may be usedto supplement the supply of electricity available to other componentsunder high demand, at the cost of consuming some stored hydrogen gas.

In order to perform in an autonomous fashion, craft 10 may include aprocessing system 46 that may include a processor 48 and a network 50 torelay data and/or commands to and from processor 48, as shownschematically in FIG. 7. Processing system 46 may be configured tocontrol each of photovoltaic system 33, storage battery 35, electrolysisapparatus 38, and the hydrogen gas handling system 40. Moreparticularly, processing system 46 may be configured to control thebuoyancy of craft 10 by increasing or decreasing the amount of hydrogencontained within envelope 26.

Autonomous craft 10 may include a navigation system 52, where thenavigation system may include one or more instruments configured todetermine the absolute or relative position of craft 10 and provide thatposition to processor 48. For example, navigation system 52 may utilizeone or more of inertial navigation, radio navigation, radar navigation,and satellite navigation (GPS), among others.

It should be appreciated that craft 10 may be useful as an unpoweredplatform, and rely upon wave action and tides (when on the water'ssurface) or prevailing winds (when aloft) for movement. Alternatively,in addition to navigation system 52, craft 10 may include a propulsionsystem 54. Any propulsion system capable of translating craft 10 in adesired direction is an appropriate propulsion system for the purposesof this disclosure. However, in order to facilitate operation in air, onthe water's surface, and beneath the surface, it may be advantageous toemploy propellers or screws for propulsion. In particular one or morepivoting ducted fans 56 may be used to direct craft 10 in the desireddirection, with the rotation speed of the propeller varied depending onwhether craft 10 is above or below the surface of the water. Thepropulsion system may be powered by the electrical network 36.

Processing system 46 may interpret the navigational data provided bynavigation system 52, and then transmit command data to the propulsionsystem 54 in order to navigate craft 10 to a desired location, such as abody of water. The location of the body of water may be stored as partof map data by the processing system, or the body of water may bedetected by a downwardly-directed optical sensor whose output may beanalyzed by optical recognition software by processing system 46.

By utilizing the processing system 46, navigation system 52, propulsionsystem 54, and the hydrogen gas handling system 40, craft 10 of thepresent disclosure may be configured to autonomously launch from thesurface of a body of water as a lighter-than-air craft, as set out inflowchart 57 of FIG. 8, by first electrolyzing water from the body ofwater to generate hydrogen gas (at 58 of flowchart 57), by adding thehydrogen gas to the deployable envelope 26 to increase the buoyancy ofcraft 10 (at 59 of flowchart 57), and by lifting craft 10 from thesurface 12 of the body of water (at 60 of flowchart 57). Craft 10 maythen subsequently descend to and be supported by the surface 12 of thesame or different body of water as a surface craft, after deflation ofenvelope 26.

Autonomous craft 10 may be further configured to operate as anautonomous submersible craft. Where craft 10 is configured to besubmersible, the craft may include a ballast system 62 that includes oneor more ballast tanks or compartments 64. For example, as shown in FIG.2, the empty interior spaces of pontoon members 22 may be configured toact as ballast compartments. Craft 10 could be rendered less buoyant bythe processing system 46 opening ballast valves and flooding the ballastcompartments 64 of craft 10, or by pumping water into the ballastcompartments. Once submerged, craft 10 could utilize propulsion system54 to proceed to a desired location or in a desired movement pattern. Tosurface, the ballast compartments 64 would be emptied, either bydisplacing the water with compressed air stored onboard, or even bycompressed hydrogen gas already available in hydrogen tank 42. Onceballast compartments 64 were empty, the ballast valves could be shut,and craft 10 could resume surface travel, or envelope 26 could beinflated and craft 10 could be launched for aerial travel. Processingsystem 46 may be additionally configured to control the buoyancy ofcraft 10 in water by varying the amount of water present in ballastcompartments 64.

In some aspects, autonomous craft 10 may further include a retractableanchor system 66. Anchor system 66 may be configured to deploy andretracted a suitable anchoring device under the control of processingsystem 46 and powered by electrical network 36. The anchoring device maybe configured to function as a conventional anchor, such that it isdeployed to the bottom of a body of water when autonomous craft 10 isresting upon its surface, in order to secure craft 10 in a desiredposition. Alternatively, or in addition, the anchoring device may beconfigured so that it could be used to maintain an absolute or relativeposition of craft 10 while it is aloft, on the surface of the body ofwater, or submerged. In particular, the anchoring device may beconfigured so that it can maintain a position for craft 10 in a mannerthat does not consume power.

For example, an appropriate anchoring device may be configured to retaincraft 10 while it is aloft above the water's surface, without requiringthe craft to alight upon the surface itself. The volume and density ofthe anchoring device may be selected so that at a particular buoyancycraft 10 can remain aloft while the anchoring device is submerged, butis nevertheless unable to lift the anchoring device from the water. Thebuoyancy of craft 10 may be readily adjusted by adding or withdrawinghydrogen from envelope 26 by processing system 46. In this aspect of thedisclosure, electrolysis apparatus 38 may obtain ambient water whilecraft 10 is aloft via the previously discussed probe or dip tube, whichmay be lowered into the water in order to aspirate water intoelectrolysis apparatus 38 as needed. In this manner the supply of waterfor producing hydrogen gas might be replenished without fully deflatingenvelope 26, which may be particularly useful when some or all of thephotovoltaic panels 34 are disposed on the envelope surface.

It should be appreciated that autonomous craft 10 may be configured tocarry any of a wide variety of payloads 70. In one aspect, craft 10 maybe used to transport relatively small or light packages when speed isnot a critical factor. Payload 70 may include mail, for example, orsmall parcels. Alternatively or in addition, payload 70 may include oneor more electronic instruments capable of recording data. Where craft 10may be used for research purposes, payload 70 may include weatherinstruments, radar equipment, sonar equipment, and tracking and/orlocator equipment for radio tags among others. Payload 70 may includeany of a variety of sensors, from visible light sensors (cameras) tonight vision cameras, infrared cameras, and other electromagneticsensors. Where the content of payload 70 requires power to function,payload 70 may be coupled to electrical network 36. Similarly, wherepayload 70 may require one or more aspects of control, payload 70 may becoupled to processing system 46.

EXAMPLES AND ALTERNATIVES

The following examples describe selected aspects of exemplary autonomouscraft. These examples are intended for illustration and should not beinterpreted as limiting the entire scope of the present disclosure. Eachexample may include one or more distinct disclosures, and/or contextualor related information, function, and/or structure.

Example 1

Hydrogen Replenishment

In one aspect of the present disclosure, the autonomous craft isprovided with an initial supply of hydrogen gas sufficient to operateautonomously. Hydrogen is notoriously difficult to retain, as it canpermeate most materials over time, therefore the craft should be able tomaintain the onboard supply of hydrogen through replenishment on bodiesof water.

Using current photovoltaic panel technologies, a photovoltaic panel 1square meter in area could generate sufficient electricity during 8hours of sunlight to generate approximately 36 grams of hydrogen.However, 36 grams of hydrogen could replenish up to 400 Liters of H₂under standard conditions, which in turn would generate almost 470 gramsof lift.

By increasing the photovoltaic panel array to 6 square meters, we wouldhave a system capable of generating 2,400 Liters of hydrogen, or 2.8 kgof lift, after 8 hours of illumination. Where the hydrogen handlingsystem and envelope of the disclosed craft loses less than 470 grams oflift per day per square meter of photovoltaic panel, the craft could intheory operate indefinitely

Example 2

This section describes additional aspects and features of the autonomouscraft of the present disclosure, and their use, presented withoutlimitation as a series of paragraphs, some or all of which may bealphanumerically designated for clarity and efficiency. Each of theseparagraphs can be combined with one or more other paragraphs, and/orwith disclosure from elsewhere in this application, in any suitablemanner. Some of the paragraphs below expressly refer to and furtherlimit other paragraphs, providing without limitation examples of some ofthe suitable combinations. Each of the paragraphs including the term“substantially” may also be provided in the same form excepting that theterm “substantially” is deleted.

A1. An autonomous craft, comprising:

a hull structure configurable to support the craft on a surface of abody of water;

an inflatable envelope coupled to the hull structure, the envelopecapable of containing an amount of hydrogen gas sufficient to render theautonomous craft lighter-than-air;

a storage battery electrically coupled to an electrical network that isconfigured to store electricity from the network and dischargeelectricity into the network;

a photovoltaic system that is coupled to the electrical network, thephotovoltaic system including one or more photovoltaic panels andconfigured to generate electricity from light on the photovoltaicpanels;

an electrolysis apparatus coupled to and powered by the electricalnetwork, configured to electrolyze ambient water to generate hydrogengas when the craft is near to or supported on the surface of the body ofwater;

a hydrogen gas handling system, including a storage tank, where the gashandling system is configured to compress and store hydrogen gasgenerated by the electrolysis apparatus in the storage tank; to releasecompressed hydrogen gas from the storage tank into the inflatableenvelope; and to compress and store hydrogen withdrawn from theinflatable envelope in the storage tank; and

a processing system configured to control the electrical network, thephotovoltaic system, the storage battery, and the electrolysisapparatus; wherein the processing system is configured to control abuoyancy of the autonomous craft by varying an amount of hydrogencontained within the envelope.

A2. The autonomous craft of paragraph A1, wherein the processing systemis configured to increase the buoyancy of the autonomous craft byincreasing the amount of hydrogen gas contained within the envelope, andto decrease the buoyancy of the autonomous craft by withdrawing hydrogengas from the envelope.A3. The autonomous craft of paragraph A2, wherein the autonomous craftis further configured to autonomously leave the surface of the body ofwater as a lighter-than-air craft and subsequently return to and besupported by the same or different body of water as a surface craft.A4. The autonomous craft of paragraph A3, wherein the autonomous craftis further configured to operate as a submersible craft.A5. The autonomous craft of paragraph A4, further comprising a ballastsystem that includes a ballast compartment and a water pumping apparatusthat is configured to fill the ballast compartment with ambient water todecrease the buoyancy of the craft, and to remove ambient water from theballast compartment to increase the buoyancy of the craft; wherein theprocessing system is additionally configured to control the buoyancy ofthe craft by varying an amount of water contained in the ballastcompartments.A6. The autonomous craft of paragraph A4, further comprising apropulsion system that is configured to propel the craft while the craftis on the surface of the body of water, while the craft is operating asa lighter-then-air craft, or while the craft is submerged, or acombination thereof.A7. The autonomous craft of paragraph A6, wherein the propulsion systemincludes one or more propellers.A8. The autonomous craft of paragraph A6, wherein the propulsion systemis coupled to and powered by the electrical network.A9. The autonomous craft of paragraph A1, further comprising a hydrogenfuel cell as an auxiliary power source.A10. The autonomous craft of paragraph A9, wherein the hydrogen fuelcell is coupled to the hydrogen gas handling system, and to theelectrical network.A11. The autonomous craft of paragraph A6, further comprising anavigation system coupled to the electrical network, wherein both thepropulsion system and the navigation system are coupled to andcontrolled by the one or more processors, so that the autonomous craftis capable of autonomous navigation and movement.A12. The autonomous craft of paragraph A11, wherein the autonomous craftis capable of autonomous navigation and movement when submerged, whenafloat, and when aloft.B1. An autonomous craft comprising:a vessel configured to alternately float upon a water surface and tofloat aloft as a lighter-then-air craft using a hydrogen gas supply forbuoyancy; the vessel including a photovoltaic array for providing powerand an electrolysis apparatus for electrolyzing water while floating onthe water surface to replenish the hydrogen gas supply.B2. The autonomous craft of paragraph B1, that includes a reversiblydeployable envelope that increases the buoyancy of the craft with theaddition of hydrogen gas in order to float aloft.B3. The autonomous craft of paragraph B1, wherein the vessel is furtherconfigured to submerge beneath the water surface.B4. The autonomous craft of paragraph B3, that includes a ballastcompartment that reduces the buoyancy of the craft when filled withwater in order to submerge beneath the water surface.B5. The autonomous craft of paragraph B1, that further includes apropulsion system capable of moving the autonomous craft while aloft,while on the water surface, or while submerged, or any combinationthereof.C1. A method of launching an unmanned aerial vehicle (UAV) having adeployable envelope from a surface of a body of water, comprising:

electrolyzing by the UAV water from the body of water to generatehydrogen gas;

adding the hydrogen gas to the deployable envelope to increase thebuoyancy of the UAV; and

lifting the UAV from the surface of the body of water.

C2. The method of paragraph C1, further comprising storing at least someof the generated hydrogen gas aboard the UAV.

C3. The method of paragraph C1, further comprising:

exposing a photovoltaic array of the UAV to incident sunlight togenerate electricity; and storing the generated electricity in a batteryaboard the UAV.

C4. The method of paragraph C3, wherein the photovoltaic array isexposed to incident sunlight while the UAV is aloft.

C5. The method of paragraph C1, further comprising:

removing hydrogen gas from the envelope to reduce buoyancy;

descending to the surface of the body of water; and

alighting upon the surface of the body of water.

C6. The method of paragraph C5, further comprising stowing the envelopeafter the UAV alights upon the surface the surface of the body of water.

C7. The method of paragraph C1, where the UAV is initially submergedbeneath the surface of the body of water, further comprising increasingthe buoyance of the UAV by removing water from a ballast compartment;and rising to the surface of the body of water before electrolyzingwater to generate hydrogen gas.C8. The method of paragraph C1, further comprising propelling theautonomous craft to a preselected destination using a navigation systemand a propulsion system of the UAV.

Advantages, Features, Benefits

The different examples of autonomous craft described herein provideseveral advantages over previous drones and unmanned vehicles.

By operating as a lighter-than-air platform, the disclosed craft canoffer an enhanced observation range, as well as an expandedcommunication range, particularly for modes of communication requiringline-of-sight.

The disclosed craft may inherently display stealthy characteristics.Detection can be minimized by rising to higher elevations, and even whenon the surface the use of electric motors would still be very quiet.Where additional stealth may be required, the craft can submerge andmove underwater.

Although stealthy operational characteristics may be advantageous formilitary applications, particularly reconnaissance, the same qualitiesare highly beneficial for some types of scientific research,particularly wildlife monitoring. A variety of research applications maybe envisioned, including underwater surveys, sea floor mapping, andtracking individual animals or social units during migration.

The disclosed autonomous craft also offer the ability to delivermaterials, such as small parcels, over long distances where speed is nota primary factor. For example, delivery of mail or medical supplies inrural areas of Africa, on isolated islands, and in generally undevelopedareas.

Conclusion

The disclosure set forth above may encompass multiple distinctdisclosures with independent utility. Although each of these disclosureshas been disclosed in its preferred form(s), the specific examplesthereof as disclosed and illustrated herein are not to be considered ina limiting sense, because numerous variations are possible. The subjectmatter of the disclosures includes all novel and nonobvious combinationsand subcombinations of the various elements, features, functions, and/orproperties disclosed herein. The following claims particularly point outcertain combinations and subcombinations regarded as novel andnonobvious. Inventions embodied in other combinations andsubcombinations of features, functions, elements, and/or properties maybe claimed in applications claiming priority from this or a relatedapplication. Such claims, whether directed to a different disclosure orto the same disclosure, and whether broader, narrower, equal, ordifferent in scope to the original claims, also are regarded as includedwithin the subject matter of the present disclosure.

What is claimed is:
 1. An autonomous craft, comprising: a hull structureconfigurable to support the craft on a surface of a body of water; aninflatable envelope coupled to the hull structure, the envelope capableof containing an amount of hydrogen gas sufficient to render theautonomous craft lighter-than-air; a storage battery electricallycoupled to an electrical network that is configured to store electricityfrom the network and discharge electricity into the network; aphotovoltaic system that is coupled to the electrical network, thephotovoltaic system including one or more photovoltaic panels andconfigured to generate electricity from light on the photovoltaicpanels; an electrolysis apparatus coupled to and powered by theelectrical network, configured to electrolyze ambient water to generatehydrogen gas when the craft is near to or supported on the surface ofthe body of water; a hydrogen gas handling system, including a storagetank, where the gas handling system is configured to compress and storehydrogen gas generated by the electrolysis apparatus in the storagetank; to release compressed hydrogen gas from the storage tank into theinflatable envelope; and to compress and store hydrogen withdrawn fromthe inflatable envelope in the storage tank; and a processing systemconfigured to control the electrical network, the photovoltaic system,the storage battery, and the electrolysis apparatus; wherein theprocessing system is configured to control a buoyancy of the autonomouscraft by varying an amount of hydrogen contained within the envelope. 2.The autonomous craft of claim 1, wherein the processing system isconfigured to increase the buoyancy of the autonomous craft byincreasing the amount of hydrogen gas contained within the envelope, andto decrease the buoyancy of the autonomous craft by withdrawing hydrogengas from the envelope.
 3. The autonomous craft of claim 2, wherein theautonomous craft is further configured to autonomously leave the surfaceof the body of water as a lighter-than-air craft and subsequently returnto and be supported by the same or different body of water as a surfacecraft.
 4. The autonomous craft of claim 3, wherein the autonomous craftis further configured to operate as a submersible craft.
 5. Theautonomous craft of claim 4, further comprising a ballast system thatincludes a ballast compartment and a water pumping apparatus that isconfigured to fill the ballast compartment with ambient water todecrease the buoyancy of the craft, and to remove ambient water from theballast compartment to increase the buoyancy of the craft; wherein theprocessing system is additionally configured to control the buoyancy ofthe craft by varying an amount of water contained in the ballastcompartments.
 6. The autonomous craft of claim 4, further comprising apropulsion system that is configured to propel the craft while the craftis on the surface of the body of water, while the craft is operating asa lighter-than-air craft, or while the craft is submerged, or acombination thereof.
 7. The autonomous craft of claim 6, wherein thepropulsion system includes one or more propellers.
 8. The autonomouscraft of claim 6, wherein the propulsion system is coupled to andpowered by the electrical network.
 9. The autonomous craft of claim 6,further comprising a navigation system coupled to the electricalnetwork, wherein both the propulsion system and the navigation systemare coupled to and controlled by the processing system, so that theautonomous craft is capable of autonomous navigation and movement. 10.The autonomous craft of claim 9, wherein the autonomous craft is capableof autonomous navigation and movement when submerged, when afloat, andwhen aloft.
 11. An autonomous craft comprising: a vessel configured toalternately float upon a water surface and to float aloft as alighter-than-air craft using a hydrogen gas supply for buoyancy; thevessel including a photovoltaic array for providing power and anelectrolysis apparatus for electrolyzing water while floating on thewater surface to replenish the hydrogen gas supply.
 12. The autonomouscraft of claim 11, including a reversibly deployable envelope thatincreases the buoyancy of the craft with the addition of hydrogen gas inorder to float aloft.
 13. The autonomous craft of claim 11, wherein thevessel is further configured to submerge beneath the water surface. 14.The autonomous craft of claim 13, including a ballast compartment thatreduces the buoyancy of the craft when filled with water in order tosubmerge beneath the water surface.
 15. The autonomous craft of claim11, further including a propulsion system capable of moving theautonomous craft while aloft, while on the water surface, or whilesubmerged, or any combination thereof.
 16. A method of launching anunmanned aerial vehicle (UAV) having a deployable envelope from asurface of a body of water, comprising: electrolyzing by the UAV waterfrom the body of water to generate hydrogen gas; adding the hydrogen gasto the deployable envelope to increase the buoyancy of the UAV; andlifting the UAV from the surface of the body of water.
 17. The method ofclaim 16, further comprising storing at least some of the generatedhydrogen gas aboard the UAV.
 18. The method of claim 16, furthercomprising: exposing a photovoltaic array of the UAV to incidentsunlight to generate electricity; and storing the generated electricityin a battery aboard the UAV.
 19. The method of claim 18, wherein thephotovoltaic array is exposed to incident sunlight while the UAV isaloft.
 20. The method of claim 16, further comprising: removing hydrogengas from the envelope to reduce buoyancy; descending to the surface ofthe body of water; and alighting upon the surface of the body of water.21. The method of claim 20, further comprising stowing the envelopeafter the UAV alights upon the surface of the body of water.
 22. Themethod of claim 16, where the UAV is initially submerged beneath thesurface of the body of water, further comprising increasing the buoyancyof the UAV by removing water from a ballast compartment; and rising tothe surface of the body of water before electrolyzing water to generatehydrogen gas.
 23. The method of claim 16, further comprising propellingthe UAV to a preselected destination using a navigation system and apropulsion system of the UAV.